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If you want to remove all elements from a collection . For example, the Foo class might have an equals method that looks like: This is considered bad practice, as it makes it very hard to implement an equals method that is symmetric and transitive.
This class defines a clone() method but the class doesn't implement Cloneable.
There are some situations in which this is OK (e.g., you want to control how subclasses can clone themselves), but just make sure that this is what you intended. In general, exceptions should be handled or reported in some way, or they should be thrown out of the method. In general, exceptions should be handled or reported in some way, or they should be thrown out of the method.
It's recommended to use the predefined library constant for code clarity and better precision. The entry Set() method is allowed to return a view of the underlying Map in which a single Entry object is reused and returned during the iteration.
As of Java 1.6, both Identity Hash Map and Enum Map did so.
When iterating through such a Map, the Entry value is only valid until you advance to the next iteration.
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If, for example, you try to pass such an entry Set to an add All method, things will go badly wrong. Random object, uses it to generate one random number, and then discards the Random object.